Coherence analysis: Methods, solutions and problems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A coherence function is a measure of the correlation of two signals and may be used as a measure for functional relationship between brain areas. In studying functional relationships, referenced EEG (REEG) coherence analysis yields important new aspects of brain activities, which complement the data obtained by power spectral analysis. However, REEG-based coherence tends to show a false high value due to volume conduction from un correlated sources (VCUS). Existing signal processing methods address this issue using a Fourier coherence function of scalp Laplacian. Although this method has been proved useful to reveal correlation between EEG signals with minimum VCUS effects, it only provides frequency-domain analysis. Since EEG signals are highly non-stationary, it is more appropriate to use time-frequency methods for coherence analysis of scalp Laplacian. Thus this research applies the wavelet transform on coherence analysis of scalp Laplacian. To verify our technique, already recorded EEG data of event related potentials were obtained from a study of two large groups of alcoholic and abstinent alcoholic subjects, performing visual picture-recognition tasks. The proposed coherence method successfully detected time-frequency correlation between EEG signals with minimum VCUS effects. It showed significant spatial specificity and revealed detailed coherence patterns. Some new important results regarding time-frequency characteristics of VCUS effects on wavelet and short-time Fourier transform (STFT) coherence analysis of REEG signals were deduced. The proposed coherence method was also compared to a conventional wavelet coherence method of REEG signals in the study of coherence difference between coherences of alcoholic and abstinent alcoholic EEG signals. Results of this study provided substantial evidence that VCUS effects are not additive and therefore can not be ignored in comparison of different brain states between groups of subjects

Coherence analysis : methods, solutions and problems

A coherence function is a measure of the correlation of two signals and may be used as a measure for functional relationship between brain areas. In studying functional relationships, referenced EEG (REEG) coherence analysis yields important new aspects of brain activities, which complement the data obtained by power spectral analysis. However, REEG-based coherence tends to show a false high value due to volume conduction from un correlated sources (VCUS). Existing signal processing methods address this issue using a Fourier coherence function of scalp Laplacian. Although this method has been proved useful to reveal correlation between EEG signals with minimum VCUS effects, it only provides frequency-domain analysis. Since EEG signals are highly non-stationary, it is more appropriate to use time-frequency methods for coherence analysis of scalp Laplacian. Thus this research applies the wavelet transform on coherence analysis of scalp Laplacian. To verify our technique, already recorded EEG data of event related potentials were obtained from a study of two large groups of alcoholic and abstinent alcoholic subjects, performing visual picture-recognition tasks. The proposed coherence method successfully detected time-frequency correlation between EEG signals with minimum VCUS effects. It showed significant spatial specificity and revealed detailed coherence patterns. Some new important results regarding time-frequency characteristics of VCUS effects on wavelet and short-time Fourier transform (STFT) coherence analysis of REEG signals were deduced. The proposed coherence method was also compared to a conventional wavelet coherence method of REEG signals in the study of coherence difference between coherences of alcoholic and abstinent alcoholic EEG signals. Results of this study provided substantial evidence that VCUS effects are not additive and therefore can not be ignored in comparison of different brain states between groups of subjects.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Emergency incisional hernia repair: a difficult problem waiting for a solution

Background Emergency repair of incarcerated incisional hernia with associated bowel obstruction in potentially or contaminated field is technically challenging due to edematous, inflamed and friable tissues with occasional need for concurrent bowel resection and carries high rates of post-operative infectious complications. The aim of this study was to retrospectively assess the wound related morbidity of use of permanent prosthetic mesh in emergency repair of incarcerated incisional hernia with associated bowel obstruction. We also describe a new technique of leaving the mesh exposed to heal by secondary intention with granulation tissue. Methods Between 2000 and 2010 a total of 60 patients underwent emergency surgery for incarcerated incisional hernia with associated bowel obstruction with placement of permanent prosthetic mesh. The wound was closed after hernia repair in 55 patients while it was left open to granulate in 5 patients. Results In the group of patients with primary wound closure, 11 patients developed superficial surgical site infection, 5 developed deep wound infection and one patient had cellulitis. These patients were treated with wound debridement and antibiotics. Mesh removal was required in one patient. There were no infections in the group of patients who had their surgical wounds left open. One patient in this group died on the fifth postoperative day from septicemia. Conclusion Use of permanent prosthetic mesh in emergency repair of incarcerated incisional hernia with associated bowel obstruction. in contaminated field is associated with high risk of wound infection

Analyzing oral communication apprehension prevailing among engineers in engineering workplace of Pakistan

Communicative apprehension affects job performance of engineers at workplace and it is never in the better interest of organizations. The purpose of this research was to investigate communication apprehension prevailing among engineers in engineering workplace of Pakistan. Five (5) engineers from 2 engineering organizations of Pakistan participated in this study. Purposive sampling method was employed since participants were drawn on specific criteria of engineers with minimum five years’ industry experience. All presentations were video recorded to explore communication apprehension traits that affected oral presentation performance of engineers. Data were analyzed qualitatively using oral presentation assessment rubric based on communication apprehension traits. This assessment rubric contained four communication apprehension traits such as oral communication skill, credibility or confidence, gestures or purposeful use of body and appearance of nervous mannerism. The results of the study revealed that due to communication apprehension engineers’ possessed poor credulity or confidence, poor gestures or purposeful use of body and faced nervousness that affected their effective oral presentation performance. The findings of this study can be used as a guideline to overcome communication apprehension of engineers through oral communication and oral presentation skill trainings in order to make them productive for organizations

Workplace Communication: Oral Communicative Competence of Engineers in Engineering Workplace of Pakistan

Communicative competence plays important role for engineers to perform workplace jobs efficiently in this wide spread business environment of organizations. The respondents of the study who participated in oral presentations were six engineers from 2 engineering workplace of Pakistan. Purposive sampling method was used for data collection purpose. Oral presentations were video recorded to capture communication strategies employed by engineers to overcome communication deficiencies during oral presentations. The data were analyzed qualitatively using strategic competence framework proposed by Canale and Swain (1980). In addition, Dornyei and Scott’s (1995) compiled Inventory of Strategic Language Devices was used to investigate types of communication strategies used by engineers to overcome their communication deficiencies during oral presentations. Open coding (Richards, 2005; Strauss and Corbin, 1998) was used to code the oral presentation data. The results of the study indicated that engineers employed four communication strategies namely message abandonment, code switching, self repetition and use of fillers. The findings of the study can be used as a guideline to add communication strategies in engineering curriculum to prepare productive engineers for modern industry. Key words: Communicative Competence, Engineers, Engineering Workplac

Analyzing Communication Apprehension of Engineering Students of Pakistan for Workplace Environment

Communication apprehension is present in academic and non academic settings that affect oral presentation performance of engineering students. The purpose of this research was to explore communication apprehension prevailing among engineering students of Pakistan. Ten (10) engineering students from two engineering universities of Pakistan participated in this study. Purposive sampling method was used since respondents were selected on specific criteria of only final year engineering students. All presentations were video recorded to capture communication apprehension related barriers that influenced effective oral presentation performance of engineering students. Data were analyzed qualitatively using oral presentation assessment rubric based on four communication apprehension traits such as oral communication skill, credibility or confidence, gestures or purposeful use of body and appearance nervous mannerism. Three assessors assessed these presentations to overcome researcher bias. The results of the study revealed that communication apprehension affected oral communication skill and credibility or confidence of engineering students. In addition, due to communication apprehension they faced nervousness during oral presentation performance. The findings of the study can be used as a guideline to overcome communication apprehension of engineering students to prepare them productive engineers for modern industry. Keywords: Communication apprehension, Engineering Workplace, Engineering student

Short run and Long run Dynamics of Macroeconomic Variables and Stock prices: Case Study of Karachi Stock Exchange.

The prime object of the study is to find the long run relationship between macroeconomic variables and prices of shares in Karachi stock exchange in Pakistan context. For this purpose the study considers the monthly data of several macroeconomic variables such as real foreign exchange rate, foreign exchange reserve, industrial production index, whole sale price index, gross fixed capital formation, and broad money M2 , these variables are obtain from 1987 to 2008 period. For the purpose of finding long run relationship among the variables Johansen co-integration test is applied. The results show that after the reforms in 1991 the influence of foreign exchanges rate and foreign exchange reserve effects significantly to stock market. The result also shows that there was positive relationship between GFCF and M2 while WPI is negative relationship with stock price. The result also highlighted that interest rate is insignificant with stock prices in the long run. The results of variance decompositions revealed that out of seven macroeconomic variables inflation showed greater forecast error for KSE 100 Index

Patient communication in radiology: current status of breaking bad news among radiologists and radiology trainees in Pakistan

Breaking bad news can be an intimidating task for any physician. The aim of this study was to record the practices of breaking bad news to the patients by Pakistani radiologists and trainees. The radiologists and trainees attending the 26th National Radiological Conference in October 2010 in Karachi, Pakistan, were surveyed. The response rate was 76%. The respondents included residents (51%), private practicing radiologists (28%), academic radiologists (13%), and other trainees (8%). Most of the academic radiologists communicated with their patients. The daily frequency of breaking bad news by residents was noted, which was highest in the public teaching hospitals (71%). For severe abnormalities such as malignancy, 50% residents, 55% of the academic radiologists and 74% of the private practicing radiologists were very uncomfortable in disclosure of results. Differences in frequency of communication with patients were noticed with both different training levels, and different settings of practice in a developing country

Volume Conduction Effects on Wavelet Cross-Bicoherence Analysis

Cross-bicoherence analysis is one of the important nonlinear signal processing tools which is used to measure quadratic phase coupling between frequencies of two different time series. It is frequently used in the diagnosis of various cognitive and neurological disorders in EEG (Electroencephalography) analysis. Volume conduction effects of various uncorrelated sources present in the brain can produce biased estimates into the estimated values of cross-bicoherence function. Previous studies have discussed volume conduction effects on coherence function which is used to measure linear relationship between EEG signals in terms of their phase and amplitude. However, volume conduction effect on crossbicoherence analysis which is quite a different technique has not been investigated up to now to the best of our knowledge. This study is divided into two major parts, the first part deals with the investigation of VCUS (Volume Conduction effects due to Uncorrelated Sources) characteristics on EEG-cross-bicoherence analysis. The simulated EEG data due to uncorrelated sources present in the brain was used in this part of study. The next part of study is based upon investigating the effects of VCUS on the statistical analysis of results of EEG-based cross-bicoherence analysis. The study provides an important clinical application because most of studies based on EEG cross-bicoherence analysis have avoided the issue of VCUS. The cross-bicoherence analysis was performed by detecting the change in MSCB (Magnitude Square CrossBicoherence Function) between EEG activities of change detection and no-change detection trials. The real EEG signals were use

Adaptation of Grid Tied Photovoltaic (GT-PV) System as Retrofit Renewable Energy Model for Single-Family House in UAE

Gulf Cooperation Countries (GCC) governments are encouraging advances in renewable energy and its deployment to reform domestic energy market policy. GCC countries including United Arab Emirates (UAE) all have begun to explore renewable energy technologies. This research intended to develop a framework model to use Grid Tied photovoltaic renewable energy (GT-PV) in the housing design of the GCC region particularly in UAE. In this regard, research has analyzed the various types of housing plans and worked out the possibilities of retrofit design to adapt renewable energy model to implement (GT-PV) in existing housing for their energy needs.  This study has determined the total energy need of each type of house, data of energy need was statically analyzed, and renewable energy output was calculated. The end result of research has surfaced a comprehensive model to design a grid-tied photovoltaic renewable energy system to cater the need for private housing in UAE